What is the treatment for ulcerative colitis (UC) affecting the descending colon to the rectum?

Treatment of Ulcerative Colitis from Descending Colon to Rectum

For ulcerative colitis affecting the descending colon to rectum, the first-line treatment should be a combination of topical mesalamine (in appropriate form for disease extent) and oral mesalamine 2-4g daily to effectively induce and maintain remission. 1, 2

Initial Treatment Algorithm Based on Disease Severity

Mild to Moderate Disease

1. First-line therapy:

   • Oral mesalamine 2-4g daily 2
   • PLUS topical mesalamine 1g daily (enemas for more proximal disease, suppositories for disease limited to rectum) 1
   • Combination therapy is more effective than either agent alone 1

2. If inadequate response after 2-4 weeks:

   • Add oral prednisolone 40mg daily 1, 2
   • Continue topical therapy as adjunctive treatment 1
   • Taper prednisolone gradually over 8 weeks according to response 1

Moderate to Severe Disease

1. Initial approach:

   • Oral prednisolone 40mg daily for prompt response 1
   • May combine with topical agents for rectal symptoms 1

2. For steroid-dependent disease:

   • Azathioprine 1.5-2.5 mg/kg/day or mercaptopurine 0.75-1.5 mg/kg/day 1

3. For severe disease requiring hospitalization:

   • IV corticosteroids (hydrocortisone 400mg/day or methylprednisolone 60mg/day) 2
   • Close monitoring with daily physical examination, vital signs, stool chart, and laboratory monitoring 1
   • Consider surgical consultation if not responding 1

Medication Selection Details

5-ASA Formulations

• Preferred agents:

  • Mesalamine 2-4g daily or balsalazide 6.75g daily 1
  • Once-daily dosing of mesalamine is as effective as multiple daily doses 2

• Alternative options:

  • Olsalazine 1.5-3g daily (note: higher incidence of diarrhea in pancolitis) 1
  • Sulphasalazine 2-4g daily (higher incidence of side effects) 1

Topical Therapy Selection

• For disease to rectosigmoid junction: Suppositories 1
• For more proximal disease: Foam or liquid enemas 1
• Note: Topical corticosteroids are less effective than topical mesalamine and should be reserved as second-line therapy for patients intolerant to topical mesalamine 1

Advanced Therapies for Refractory Disease

For patients failing conventional therapy:

1. Biological agents:

   • Infliximab 5 mg/kg at weeks 0,2, and 6, followed by maintenance every 8 weeks 3
   • Clinical response rates of 65-69% at week 8 with infliximab 3

2. Other advanced options:

   • Anti-TNF agents, anti-integrin, IL-12/23 inhibitor, JAK inhibitors, or S1P receptor modulators 2, 4

Maintenance Therapy

• Lifelong maintenance therapy is generally recommended for all patients, especially those with left-sided disease 1
• Recommended maintenance:
  • Mesalamine ≥2g/day to reduce risk of relapse and colorectal cancer 2
  • For frequent relapses: consider azathioprine 1.5-2.5 mg/kg/day or mercaptopurine 0.75-1.5 mg/kg/day 1, 2

Important Considerations and Pitfalls

• Proximal constipation should be treated with stool bulking agents or laxatives 1
• Monitor for complications:
  • Regular monitoring of renal function with 5-ASA therapy 2
  • Colonoscopy surveillance beginning 8 years after diagnosis for dysplasia 4
• Avoid common pitfalls:
  • Too rapid reduction of corticosteroids is associated with early relapse 1
  • Long-term treatment with steroids is undesirable due to side effects 1
  • Inadequate dosing of mesalamine (4.8g/day is more effective than 2.4g/day for active disease) 5

Special Situations

• Severe disease requiring hospitalization:

  • IV fluid and electrolyte replacement
  • Blood transfusion to maintain hemoglobin >10 g/dl
  • Subcutaneous heparin for thromboembolism prophylaxis
  • Nutritional support if malnourished 1, 2

• Consider surgery if:

  • Refractory to maximal medical therapy
  • Development of toxic megacolon, perforation, or severe bleeding 6

By following this treatment algorithm based on disease severity and extent, most patients with ulcerative colitis affecting the descending colon to rectum can achieve clinical remission and maintain a good quality of life.